The invention relates to an improved engine unit for a motor vehicle and more particularly to an improved cam drive system for such an engine.
As is well known, the spatial requirements of motors for vehicles are critical. This is due to the increased complexity of the engines, transmissions and the number of accessories driven by the engine. Also, the configuration of modern motor vehicles and their streamlining dictates relatively small and sometimes undesirable configurations for the engine compartment in order to achieve the overall design effects of the vehicle.
In order to achieve low hood lines and better streamlining, resort has been made to positioning the engine transversely in the engine compartment in a front engine, front wheel drive vehicle. Of course, such transverse engine locations in rear engine, rear wheel drive vehicles are also widely used. Nevertheless, even though such an orientation can improve the layout of the engine compartment, there is still a problem in connection with the length of the engine. Specifically, it is extremely important that the length of the engine, the portion extending transversely across the engine compartment, is short.
As is well known, the power output of an engine and its efficiency can be increased if one or more overhead mounted camshafts are employed for operating the valve train. Conventionally, such camshafts are driven off one end of the crankshaft. This design has been replaced by driving the camshafts through an intermediate cam drive shaft completely journalled in the cylinder head. However, by journalling the intermediate cam drive shaft in the cylinder head manufacturing and assembly difficulties arise. For instance, because of the proximity of the journal housing to the air intake region it is very difficult to locate the manufacturing means correctly with respect to the cylinder head. Further, because the journal housing is integral with the cylinder head the accessibility for maintenance or service is diminished.
It is, therefore, a principal object of this invention to provide an improved camshaft drive arrangement for an internal combustion engine.